There currently is interest in having low frequency directional antennas in space. Two design concepts for such an antenna have gained attention. One is a flat phased array. The other is a parabolic dish which mechanically scans. The flat array has the disadvantage that when one steers its beam to the horizon (as one must do to avoid direct reflections from the earth) it sacrifices power (loses effective aperture), about 3 db worth. The parabolic antenna, in order to scan, must be constantly in motion, and this motion must be controlled to an extraordinarily fine degree in order to maintain the antenna properly oriented, and hence effective. This is an extraordinarily difficult engineering task, the solution to which would be a complicated and expensive control system.
Large diameter deployable loop antennas have been developed for use in space. For example, U.S. Pat. No. 4,811,033 (Ahl et al) discloses a space-based antenna generally in the shape of an umbrella wherein the "umbrella" surface comprises parabolic RF reflectors. The antenna is deployed from a stowed configuration the surface contour of the loop antenna elements is automatically controlled. U.S. Pat. No. 4,578,920 (Bush et al) is directed to a space-based antenna including a collapsible-expandable supporting truss structure. Other relevant patents include U.S. Pat. No. 4,757,323 (Duret et al), U.S. Pat. Nos. 4,658,261 (Reid et al) and 4,814,784 (Pallmeyer.)